5 Mechanical works In the following mechanical works it is assumed that all are in situ overhauls and that the items considered are all accessible for the work to be performed. If any item is to be removed ashore to the workshops then an assessment of the work involved must be made and the rates given amended accordingly. This is considering removals to permit trans- portation of the item from the ship and their later refitment, on com- pletion of the reinstallation. Mechanical works 41 ch001.qxd 28/7/00 11:36 am Page 41 Overhauling diesel engines (single-acting, slow-running, two-stroke, cross-head) In the overhauling of large main propulsion engines, it is assumed that the ship will provide all the specialized equipment necessary. This refers to heavy-duty equipment which is normally supplied by the engine manufacturer and also any special hydraulic tensioning equipment for fastenings. In main engines, it is assumed that there are lifting devices such as overhead beams, runner blocks and/or overhead cranes. 42 Guide to Ship Repair Estimates (in Man-hours) Figure 8 A main propulsion diesel engine ch001.qxd 28/7/00 11:36 am Page 42 Table 5.1 Top overhaul Disconnect and remove cylinder head, withdraw piston, remove piston rings, clean, calibrate and reassemble as before using all owner’s supplied spares. Cylinder bore (mm) Man-hours per cylinder 500 67 550 70 600 75 650 80 700 87 750 95 800 105 850 115 900 125 950 137 1000 150 Cylinder cover Disconnect and remove cylinder head, clean all exposed parts, including piston crown and reassemble as before using all owner’s supplied spares. Assume as 60% the rate of top overhaul rate. Mechanical works 43 ch001.qxd 28/7/00 11:36 am Page 43 Table 5.2 Cylinder liners – 1 Withdrawing of cylinder liner, cleaning exposed areas as far as accessible, installing of new, owner’s supplied liner and rubber seals. Cylinder bore (mm) Man-hours per cylinder 500 60 550 62 600 67 650 72 700 77 750 82 800 90 850 97 900 107 950 120 1000 135 Note: Assuming that cylinder head, piston and piston rod are already removed as part of the top or complete overhaul. 44 Guide to Ship Repair Estimates (in Man-hours) ch001.qxd 28/7/00 11:36 am Page 44 Table 5.3 Bearing survey – 1 Opening up for inspection, exposing both halves, cleaning, calibrat- ing and presenting for survey. On completion, reassembling as before. Man-hours/bearing Cylinder bore (mm) Cross-head Crank pin Main 500 47 32 45 550 50 35 48 600 52 37 50 650 55 40 52 700 57 42 55 750 58 45 56 800 60 47 59 850 62 50 63 900 65 52 67 950 68 55 72 1000 72 57 76 1050 75 60 80 Note: For exposing top half of bearing shell only, charge 60% of above rates. Table 5.4 Crankshaft deflections – 1 (a) Opening up crankcase door for access works and refitting on completion. (b) Setting up deflection indicator gauge, turning engine, using ship’s powered turning gear and recording observed readings. Removing equipment and closing up crankcase door on com- pletion. Mechanical works 45 ch001.qxd 28/7/00 11:36 am Page 45 Cylinder bore (mm) (a) Deflections (b) Crankcase doors Man-hours per unit Man-hours per door > 750 4 4 750–850 4.5 4.5 850–950 4.5 5 950–1050 5 5.5 46 Guide to Ship Repair Estimates (in Man-hours) ch001.qxd 28/7/00 11:36 am Page 46 Overhauling diesel engines (single-acting, slow-running, in-line, four-stroke, trunk) In the overhauling of large main propulsion engines it is assumed that the ship will provide all the specialized equipment necessary. This refers to heavy-duty equipment which is normally supplied by the engine manufacturer and also any special hydraulic tensioning equipment for fastenings. In main engines, it is assumed that there are lifting devices such as overhead beams, runner blocks and/or overhead cranes. Mechanical works 47 Figure 9 A ship’s medium-speed main engine ch001.qxd 28/7/00 11:36 am Page 47 Table 5.5 Four-stroke trunk-type main engines (a) Cylinder head: Disconnecting and removing cylinder head, clean- ing all exposed parts, including piston crown and reassembling as before using all owner’s supplied spares. Disconnecting and remov- ing 2 in number air inlet valves and 2 in number exhaust valves, including exhaust valve cage with removable seats. Cleaning and decarbonizing valves, cages and head as far as accessible, lightly hand grinding valves for examination only of seating areas. (a) Clarifications: (a) Work on the seats may be protracted so is excluded. This could include changing seat inserts, machining and grinding/lapping seats. It will require establishing and should be subject to work assessment. (b) Top overhaul: Disconnect and remove one pair of crankcase doors, disconnect bottom end bearing fastenings. Disconnect and remove cylinder head, withdraw piston, remove piston rings, clean, cali- brate and reassemble as before using all owner’s supplied spares. (c) Piston gudgeon pin: Drawing out gudgeon pin from removed piston, clean all exposed parts, calibrate and record and reinstall pin as before. Any spares to be owner’s supply. Cylinder bore (a) Man-hours (b) Man-hours c) Man-hours (mm) per cylinder head per cylinder per piston pin 100 16 16 4 150 20 20 4 200 22 24 6 250 24 32 8 300 32 36 10 350 36 40 12 400 40 48 14 450 48 56 16 500 56 64 18 550 64 72 20 600 72 80 24 Note: For Vee bank engines add 20% per unit. 48 Guide to Ship Repair Estimates (in Man-hours) ch001.qxd 28/7/00 11:36 am Page 48 Table 5.6 Cylinder liners – 2 Withdrawing of cylinder liner, cleaning and painting exposed areas as far as accessible, installing of new, owner’s supplied liner, or exist- ing liner, complete with owner’s supplied rubber seals and top joint. Attending hydrostatic test carried out by ship’s staff. Cylinder bore (mm) Man-hours per cylinder 100 16 150 20 200 24 250 28 300 32 350 40 400 44 450 48 500 52 550 56 600 60 Mechanical works 49 ch001.qxd 28/7/00 11:36 am Page 49 Table 5.7 Bearing survey – 2 Opening up for inspection, exposing both halves, cleaning, calibrating and presenting for survey. On completion, reassembling as before. Man-hours per bearing Cylinder bore (mm) Crank pin Main 100 6 4 150 8 6 200 10 8 250 14 10 300 16 12 350 18 14 400 20 16 450 24 18 500 28 20 550 32 24 600 36 32 Note: For exposing top half of bearing shell only, charge 60% of above rates. 50 Guide to Ship Repair Estimates (in Man-hours) ch001.qxd 28/7/00 11:36 am Page 50 . 48 60 0 52 37 50 65 0 55 40 52 700 57 42 55 750 58 45 56 800 60 47 59 850 62 50 63 900 65 52 67 950 68 55 72 1000 72 57 76 1050 75 60 80 Note: For exposing top half of bearing shell only, charge 60 %. 36 40 12 400 40 48 14 450 48 56 16 500 56 64 18 550 64 72 20 60 0 72 80 24 Note: For Vee bank engines add 20% per unit. 48 Guide to Ship Repair Estimates (in Man-hours) ch001.qxd 28/7/00 11: 36. Main 100 6 4 150 8 6 200 10 8 250 14 10 300 16 12 350 18 14 400 20 16 450 24 18 500 28 20 550 32 24 60 0 36 32 Note: For exposing top half of bearing shell only, charge 60 % of above rates. 50 Guide to